<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    body{
      padding: 0;
      margin: 0;
    }
    .box{
      background-color: #000;
      position: fixed;
      width: 100%;
      height: 100%;
    }
  </style>
</head>
<body>
  <div class="box"></div>
</body>
</html>